Restrict special character and space in Input field

inputRestrictions.js

function userValidation(val,event) {

    var k = event ? event.which : window.event.keyCode;
    var len = val.length;
    if (len == 0 && k == 32){
        return false;
    }

  //Restrict spacial character
  // 45 = hyphen (-), 46 = fulls top (.), 95 = underscore (_), 48-57 = 0-9, 65-90 = Uppercase alphabets 97-122 = Lowercase alphabets
    if (!((k >= 48 && k <= 57) || (k >= 65 && k <= 90) || (k >= 97 && k <= 122) || k == 46 || k == 45 || k == 95 || k == 32)) {
        return false;
    }

  //Reducing the length by 1 to get previously entered input
  //This will restrict user from entering multiple spaces
    len--;
    if(val.charAt(len) == " " && k == 32){
        return false;
    }

}